(X3 V11) - Sales Order created through web service with incorrect totals (random error)

SOLVED

A client is having the following issue:

They are using a third party application to send web orders to X3 (most of their orders are web orders). The Sales Orders are created properly about 95% of the time but here and there an order ends up in X3 with a wrong valuation for no apparent reason. For instance a $0 Order is created with a total amount of $1306 (completely random number). When deleting this order and re-sending it to X3 the second time, the totals are correct (even after re-sending it 5-10 times). Because this error happens randomly, it has been impossible to debug it. It seems like the error somehow happens in the standard valuation logic. The work-around so far has been to go to the Order in X3, click any line and press "Enter" to force the re-calculation of the totals then save.

My question is: Has anybody else noticed a similar case before, where SOs created through web services randomly end up in X3 with incorrect taxes or totals?

Thanks,

Seb